Govt denies Defence HQ cost cover-up

The Federal Government has rejected Opposition accusations it is hiding the cost of the Defence headquarters planned for near Bungendore in southern New South Wales.

The Opposition has questioned why there was no money allocated in the Federal Budget for the joint operations command HQ.

But the Special Minister of State and local MP Gary Nairn says a private organisation will build the centre, so no costs will appear in the Budget until the Government begins leasing the building back.

Mr Nairn says an announcement on the successful tenderer for the multi-million dollar project will happen soon.

"As I understand it there will be an announcement hopefully not too far away," he said.

"I know I mentioned ... informally the other day that it should be happening soon, but as I said, it's a huge project, huge contract and all the t's have got to be crossed and the i's have got to be dotted before an announcement can be made."